Can compost reduce diseases in potato?

Posted on Sep 1 2020 by Sam Le Gallou

Soil science honours opportunities are available for students to investigate the potential of compost to reduce diseases and improve potato yield and quality.

Diseases such as black dot are a threat to the potato industry because they reduce yield and result in waste as affected potatoes don’t meet market requirements. To reduce disease incidence, most potato producers can grow potatoes only every 3-5 years in the one paddock. Shorter rotation times result in high disease incidence. Some producers fumigate the soil to reduce rotation times, but fumigation also kills beneficial soil organisms and therefore threatens soil health and sustainability.

Irrigation is another important cost factor in the potato industry. However, irrigation water is often wasted because the soils have a low water-holding capacity and can be non-wetting.

Compost application could address both issues. For example, it may reduce disease incidence and increase soil water holding capacity with additional benefits such as improved nutrient supply and thus reduced fertiliser need and improved soil health.

Indeed, some potato producers have applied compost as organic fertiliser and found that yields were improved. There are reports from other crops that show that high rates of compost application can reduce disease incidence. However, there are no detailed investigations about this in Australian potato growing regions.

Aims and outcomes

The aim of this project is to develop a compost amendment for potatoes that:

reduces soil borne diseases; and
improves soil water holding capacity and nutrient supply.

Predicted outcomes will be shorter rotation times, higher yield, waste reduction, increased irrigation efficiency and overall increased productivity.

Methodology

Soil with known history of black dot will be collected in the field and amended with compost. In pot experiments, compost rates, forms and composition will be tested.
Parameters studied include disease incidence (PREDICTA-PT from SARDI), soil water holding capacity, and potato yield.